One important area in the technical field of mobile radio communications relates to the handover (HO) of User Equipment (UE) from a (serving) source cell to a (neighboring) target cell and the optimization of parameters controlling the HO. In this technical field Self Optimizing Networks (SON) and in particular Mobility Robustness Optimization (MRO) are objects of high interest.
Traditionally, the optimization of network configuration parameters in 2G or 3G mobile radio communication networks is based on labor- and cost-intensive drive testing. For a first roll-out, network-wide default configuration parameters are used and if performance management (PM) counters are accumulating Radio Link Failures (RLFs) or even call drops in certain service areas, several optimization loops with drive testing equipment have to be accomplished in order to adapt parameters in a proper and cell-specific manner.
The object of MRO is to automate the optimization of those network configuration parameters, which are triggering a HO, such that first and foremost Radio Link Failures (RLFs) and HO failures (HOF) are reduced and secondly also unnecessary HOs like (a) so called ping pong HOs, which occur in particular if a UE is located within a border region between two base stations, and/or (b) so called short stays of a UE with a certain base station (BS) are prevented.
HO problems which might even cause RLFs may occur in case the HO thresholds being used have inappropriate values. 3GPP has specified three different categories of HO problems which may cause a RLF:
(a) Failures due to too late HO triggering
(b) Failures due to too early HO triggering
(c) Failures due to HO to a wrong cell
A MRO procedure typically consists of two phases: A Root Cause Analysis (RCA) phase and a correction phase. In a RCA phase all information which is needed in order to analyze a mobility problem is brought together in order to generate corresponding cell or cell-pair specific statistics of Key Performance Indicator (KPI). In a correction phase based on the KPI statistics appropriate countermeasures are determined and measurement parameters triggering a HO are adjusted accordingly.
There may be a need for improving the handover behavior of a mobile radio communication network.